Photo interupter module use the buildin arduino led. If the sensor is broken the LED is turned on.
Device senses a signal, LED lights, otherwise off.
If you view from the top like on the photo
Connect the module to the arduino as follows:
// Example code for KY-010
// photo interrupter module
 
int Led = 13 ;// define LED Interface
int buttonpin = 3; // define the photo interrupter sensor interface
int val ;// define numeric variables val
void setup ()
{
  pinMode (Led, OUTPUT) ;// define LED as output interface
  pinMode (buttonpin, INPUT) ;// define the photo interrupter sensor output interface   
}
void loop ()
{
  val = digitalRead (buttonpin) ;// digital interface will be assigned a value of 3 to read val
  if (val == HIGH) // When the light sensor detects a signal is interrupted, LED flashes
  {
    digitalWrite (Led, HIGH);
  }	else {
    digitalWrite (Led, LOW);
  }
}